The prediction of behaviour of ashes from five different solid fuels in fluidised bed combustion

The behaviour of different ashes was predicted by the combination of extend ed fuel analysis with advanced global thermodynamic equilibrium calculation s. The extended fuel analysis is a fractionation method that consists of se quential leaching of a solid fuel with water, ammonium acetate and hydrochl oric acid. In order to cover a broad spectrum of fuels a coal, a peat, a fo rest residue and Salix (i.e. willow) were studied. The last was taken with and without soil contamination, i.e. with a high and low content of silica, respectively. Results from the fractionation showed clear differences in mineral distribu tion in the fuels. More ash-forming elements were present as included miner als in the older fuels. In relatively young fuels, almost half of the inorg anic material was found in the soluble fractions after leaching with water and ammonium acetate. Fouling and slagging predictions based on the combine d use of the extended fuel analysis and the advanced global equilibrium ana lysis indicated that no ash-related problems should be expected in FBC boil ers firing the studied coal. The peat that was studied could cause minor as h depositions in the flue gas channel at temperatures above 700 degrees C. The studied forest residue could form fly ash deposits in the flue gas chan nel at temperatures between 600 and 860 degrees C. The Salix could cause fl y ash depositions at temperatures between 840 and approximately 1000 degree s C. If soil contamination was present as well, Salix could cause bed sinte ring at temperatures above 1030 degrees C. (C) 2000 Elsevier Science Ltd. A ll rights reserved.